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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
399 of 808
NXP Semiconductors
UM10360
Chapter 18: LPC17xx SSP0/1 interface
6.5 SSPn Clock Prescale Register (SSP0CPSR - 0x4008 8010, SSP1CPSR
- 0x4003 0010)
This register controls the factor by which the Prescaler divides the SSP peripheral clock
SSP_PCLK to yield the prescaler clock that is, in turn, divided by the SCR factor in
SSPnCR0, to determine the bit clock.
Important:
the SSPnCPSR value must be properly initialized or the SSP controller will not
be able to transmit data correctly.
In Slave mode, the SSP clock rate provided by the master must not exceed 1/12 of the
SSP peripheral clock selected in
. The content of the SSPnCPSR register is
not relevant.
In master mode, CPSDVSR
min
= 2 or larger (even numbers only).
6.6 SSPn Interrupt Mask Set/Clear Register (SSP0IMSC - 0x4008 8014,
SSP1IMSC - 0x4003 0014)
This register controls whether each of the four possible interrupt conditions in the SSP
controller are enabled. Note that ARM uses the word “masked” in the opposite sense from
classic computer terminology, in which “masked” meant “disabled”. ARM uses the word
“masked” to mean “enabled”. To avoid confusion we will not use the word “masked”.
3
RFF
Receive FIFO Full. This bit is 1 if the Receive FIFO is full, 0 if
not.
0
4
BSY
Busy. This bit is 0 if the SSPn controller is idle, or 1 if it is
currently sending/receiving a frame and/or the Tx FIFO is not
empty.
0
7:5
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
NA
Table 353: SSPn Status Register (SSP0SR - address 0x4008 800C, SSP1SR - 0x4003 000C)
bit description
Bit
Symbol
Description
Reset Value
Table 354: SSPn Clock Prescale Register (SSP0CPSR - address 0x4008 8010, SSP1CPSR -
0x4003 8010) bit description
Bit
Symbol
Description
Reset Value
7:0
CPSDVSR This even value between 2 and 254, by which SSP_PCLK is
divided to yield the prescaler output clock. Bit 0 always reads
as 0.
0